Pneumatic seal-crimping tool for tensioned strapping loops

ABSTRACT

A trigger-actuated pneumatic tool for crimping a metal seal around the overlapping portions of a tensioned strapping loop, utilizing a pair of piston-actuated crimping jaws to compress the seal. Full crimping depth is assured by a pneumatic control arrangement whereby the crimping jaws will not release the seal until the latter has been fully crimped. A secondary feature resides in a particular jaw structure which enables a shorter piston stroke to effect a full seal crimp, thereby reducing tool height and weight.

United States Patent Inventor Larry D. Plunkett Crystal Lake, 111.

Appl. No, 782,533

Filed Dec. 10, 1968 Patented Jan. 5, 1971 Assignee Signode CorporationChicago, III. a corporation of Delaware PNEUMATIC SEAL-CRIMPING TOOL FORTENSIONED STRAPPING LOOPS Claims, 10 Drawing Figs.

[52] U.S. Cl. 140/934 [51] Int. Cl B2lf9/02, B2lf /06 Field ofSearch81/9.1l-l, 9.1M; /30; /932, 93.4, 93.6

[56] References Cited UNITED STATES PATENTS 2,752,807 7/1956 Gregory81/9.l

2,831,381 4/1958 Lingle 8l/9.1 2,974,551 3/1961 Powell... 8l/9.l

2,996,939 8/1961 Meier 8l/9.1 3,329,178 7/1967 Plunkett 140/9343,334,695 8/1967 Rosenberger et al. 140/934 Primary ExaminerCharles W.Lanham Assistant Examiner-E. M. Combs Attorney-Edward R. LowndesABSTRACT: A trigger-actuated pneumatic tool for crimping a metal sealaround the overlapping portions of a tensioned strapping loop, utilizinga pair of piston-actuated crimping jaws to compress the seal. Fullcrimping depth is assured by a pneumatic control arrangement whereby thecrimping jaws will not release the seal until the latter has been fullycrimped.

A secondary feature resides in a particular jaw structure which enablesa shorter piston stroke to effect a full seal crimp, thereby reducingtool height and weight.

"u u-sqpq" PATENTEUJAN SIB?! 3.5521450 SHEET 1 OF 3 F1612 INVENTOR LARRY0. PLUNKETT PATENTEU m m.

SHEET 3 OF 3 T'FIGI'8- //v vE/v T0R LARRY 0. PLUNKETT By iemd. 0 ink- Mpart of this specification, one illustrative tled Crimping Mechanism.

Air-powered crimping tools of the type under consideration, and asexemplified by the aforementioned patent to Meier, are possessed ofcertain limitations, principal among which is the inability of suchtools (or sealers as they are commonly. referredto) to provide anadequate safeguard against impropersealing. Forexample, in assembly linework where rapid and repetitive sealing is desirable, a drop in air linepressure below a predetermined minimum will be reflected by theinability of the piston-actuated sealing jaws of the sealer to carry thecrimping operation tothe full seal-crimping depth, thus resulting in anunsafe and only partially crimped seal. Upon release of the actuatingtrigger by means of whichair is conducted to the sealing cylinder,the'sealing jaws will open and release the partially crimped seal so thatthe operator may proceed withthe next-succeeding sealing operation. Thedif ference, appearancewise, between a fully crimped seal and one whichis only partially crimped is seldom apparent and, as a consequence, inthe past, dangerous situations have 'occurred where a long succession ofbundles have left the sealing area in an unsafe condition.. I

The present invention is designed to overcome the above noted limitationthat is attendant upon conventional sealers and, toward this end, theinvention contemplates the provision of a sealer which has associatedtherewith novel means.

whereby, in the event of adecre'ase in air line pressure below thepredetermined. safe minimum, orfor any other reason whatsoeverthesealing jaws fail to traverse their full seal crimping stroke,release of the actuating trigger will fail to initiate the jaw-openingoperation so that the operator may not detach the tool from the sealuntil remedial measures have been taken, as for example by restoringfull air line pressure,

FIG. 4 is a side elevational view similar to FIG. 1 showing the parts inthe positions which they assume when partial seal crimping has beeneffected;

FIG. 5 is a top plan view similar to FIG. 2 but representing the partsin the positions they assume in FIG. 4;

FIG. 6 is a fragmentary side elevational view, largely in verticalsection and similar to FIG. 4, showing the parts in the positions whichthey assume when full and effective sealcrimping operations have beencompleted;

FIG. 7 is a top plan view similar to FIGS. 2, 4 and 5, showing the partsin the positions-which they assume upon completion of the seal-crimpingoperation;

or by manipulating a special jaw-release finger which,'

although effective to release the jaws from the seal, places theoperator on notice: that the particular seal is defectively crimped.

Another limitation that is attendant upon conventional sealers of the.type under consideration is concerned with a matter of overalltooldimensions wherein the effective stroke of the jaw-actuating pistonand the expansion stroke of the toggle linkage associated with thesealing jaws and piston are additive factors which contribute towardoverall tool height.

According to the present invention; by the use of a novel jaw tion.Other objects and advantages, not at this time enumerated, will readilysuggest themselves as the nature of the invention is better understood.

In the accompanying three sheets of drawings forming a embodiment of theinvention has been shown.

In these drawings:

FIG. 1 isa side elevational view of the improved pneumatic seal-crimpingtool with a portion of the tool casing broken FIG. 3 is an end view ofthe structure shown in FIGS. 1 and a FIG. 8 is a sectional view takensubstantially along the line 8-8 of FIG. 1;

FIG. 9 is a perspective view of a metal seal operatively positioned onthe overlapping portions of a strapping loop preparatory to theseal-crimping operation; and

FIG. 10 is a perspective view of a fully and twice-crimped seal, showingthe same effectively applied to the overlapping portions of thestrapping loop.

Referring now to the drawings in detail and in particular to FIGSi l and2, a seal-crimping tool embodying the principles of the presentinvention has been designated in its entirety at 10. This tool is of thegeneral type shown and described in the aforementioned U.S. Pat. toMeier, No. 2,996,939 and is designed for the same purpose, namely tocrimp a metal seal sueh as has been shown at S in FIG. 9 about theoverlapping portions 12 and 14 of a loop L of metal strapping which hasbeen tensioned and remains under tension while the sealcrimpingoperation is being effected. Both the tools of the Meier patentand thatof the present invention operate upon the seal S to produce-a crimpedseal such as is shown in FIG. 10 wherein .the tool is applied to theseal S twice to produce offset deformations at 15 along the oppositeedge regions of the seal. These deformations are created by means of twoopposed pairs of jaws 16 (FIG. 2) which swing beneath the seal S andeffectively force the'inturned seal flanges 18 upwardly so as todisplace the strapping laminae l2 and 14, as well as the crown portion20 of the seal, tobend localized areas of the seal and strapping aroundthe bottom edge of a notcher bar 22 which is centered between the twojaws and acts as a fixed reaction member during such metal bendingoperations, all in a manner that will become clear when the nature ofthe strapping tool 10 is better understood.

Considering now the crimping tool or sealer 10, this tool is of theair-operated pistol-grip-type and involves in its general organization ahand grip 30 having a trigger 32 and supporting a cylinder 34 which isintegral therewith and the forward end of which is closed by a mountingplate 36 having a pair of forwardly extending attachment lugs.38. Themounting plate 36 is secured to the forward open rim of the cylinder 34by means of screws 40. The mounting lugs 40 serve as a support for acrimping jaw assembly 42 which is operable under the control of a piston44 reciprocable in the cylinder 34.

' Still referring to FIGS. 1 and 2,the crimping tool 10 may be regardedas being comprised of three principal sections, the crimping jawassembly 42 constituting a jaw section, the piston 44 and cylinder 34,together with their adjuncts, constituting a cylinder section foractuating the jaw section, and the pistol grip 30 constituting a controlvalve section for supplying air to the cylinder section in a selectivemanner to control the operation of the latter.

The jaw section which comprises the jaw assembly 42 includes a pair ofside plates 50 and 52 which extend in parallelism, are identical inconfiguration, and are secured to the mounting plate 36 by bolts 54which pass through the mounting lugs 40. The aforementioned notcher bar22 is carried at the forward ends of the side plates by-means of atransversely extending bolt 56 and a pair of transverse pins 58, thelatter constituting pivot pins for two pairs of jaw members 60, therebeing one pair on each side of the notcher bar 22 so that the jawmembers serve as spacer members as clearly shown in FIG. 3 formaintaining the notcher bair in a central position between the two sideplates 50 and 52. The aforementioned crimping jaws 16 are disposed atthe extreme forward ends of the jaw members 60.

The mounting plate 36 is formed with a centrally disposed, rearwardlyextending circular boss 62 having a generally square opening 64extending therethrough (FIG. 8), the latter communicating with theinterior of the cylinder 34. A pair of opposed rearward extensions 66 onthe side plates project into the opening 64, each extension beingrecessed to provide a longitudinally extending guideway 68 for a pair ofpin-retaining plates 70 the function of which will be made clearpresently.

The various jaw members 60 are in the form of elongated links and thepivot pins 58 are disposed in close proximity to the jaw members 16. Inthe normal position of the jaw members 60 they are disposed entirelywithin the generally rectangular confines of the two side plates 50 and52 and the rear ends thereof are pivotally connected by pins 72 to theforward ends of a pair of spreader links 74, there being one spreaderlink for each pair of adjacent jaw members 60. The rear ends of the twospreader links 74 are pivotally connected together for movement inunison by means of a pivot pin 76 which constitutes an element of acrosshead assembly 78.

It is to be noted at this point that the two spreader links 74 are eachgenerally of J-shape design, each link having proximate portions 80which normally extend in close proximity .and parallelism, and distalportions 82 which cross each other and extend outwardly in divergentfashion. By such an arrangement the respective vectorial thrust exertedby the spreader links 74 upon the jaw members 60 during forward travelof the crosshead 78 is such that the links 74 will spread the rear endsof the jaw members 60 apart, despite the fact that normally the jawmembers are inclined toward each other in a' rearward direction. Statedotherwise, the toggle joint which is established by the jaw members andspreader links is piston rod 92 which is provided with a forward forkedend 94,

thfork tines of which straddle the rear pivoted ends of the spreaderlinks 80 and receive therethrough the reduced end regions of the pin 76.By such an arrangement, the two plates '70 confine the pivot pin 76therebetween and prevent axial shifting of the pin and possibledislodgment thereof at such time as the piston is in a retractedposition and the pins have moved outside of the confines of theguideways 68 associated with the boss 62. The piston 44 is normallymaintained in its fully retracted position as shown in H68. 1 and 2 bymeans of a compression spring 96 which encircles the piston rod 92, ispiloted at its forward end by the circular boss 62, and bears at itsrear end against the piston.

Although .the tool 10 has been illustrated as being assembled so thatthe jaw members 60 and spreader links 80 operate in a plane which is ata right angle to the general plane of the hand grip 32, it will beunderstood that by removing the fastening screws 40 and rotating themounting plate 36, together with its supported jaw assembly 42 in eitherdirection, the jaw members 60 and links may be caused to operate, afterreplacement of the screws 40, in the plane ofthe hand grip.

When the tool is applied to a seal S for the purpose of crimping thesame about the overlapping portions 12 and 14 ofa strapping loop L, thetool is manipulated initially so that the sealingjaws 16 straddle theside edges of the seal while the crown portion of the seal is engaged bythe notcher bar 22 as clearly shown in FIG. 2. Assuming that full ratedair line pressure is admitted to the rear end of the cylinder 34 fordriving the piston 44 forwardly, the initial movement of the piston willeffect a spreading movement of the toggle joint which is established bythe various spreader links 74 and jaw members 60 so that the latterswing in opposite directions about their pivotal axes 58 and cause thejaws 16 to close upon the seal. Initial engagement of the seal by thejaws 16 takes place at spaced apart regions along the seal flanges 18and, as shown in FIG. 5, the seal S as a whole is clamped between thesejaws 16 and the forward recessed edge of the notcher bar 22. Becausefull rated air line pressure is supplied to the' cylinder 34, continuedclosing movement of the jaws 16 will then initiate the actualseal-crimping operation wherein the jaws 16 displace the metal of theseal flanges 18 and force the same against the overlapping strappinglaminae, as well as against the longitudinal edge regions of the crownportion 20 of the seal. Since the forward edge of the notcher bar servesas a reaction anvil against the medial region of the crown portion ofthe seal, the side edges of the seal and strapping become crimped by apartial wrapping of the seal and its container strapping around theforward edge of the notcher bar 22 to produce a single pari ofoppositely disposed depressions such as are shown at 15 in FIG. 10.During a succeeding'operation of the tool, a second pair of suchdepressions 15 will beformed alongside the first pair, it beingconsidered good crimping practice to crimp each seal S twice.

Upon bleeding of the rear end of the cylinder 34 to the atmosphere afterthe seal has been fully crimped, the spring 96 will restore the pistonto its fully retracted position, thus mov-- ing the crosshead assembly78 rearwardly and collapsing the aforementioned toggle joint associatedwith the crimping jaws 16 to open the latter and release the jaws fromthe crimped seal.

According to the present invention, means are provided whereby in theevent of failure of the crimping jaws 16 to effect full depth ofcrimping, the crimping jaws 16 are prevented from releasing the seal sothat the tool may not inadvertently be put to use for a succeedingcrimping operation. This means is in the form of a novel latch mechanismassociated with the control valve section 30 of the tool and nature andoperation of which will be described in detail subsequently.

Considering now the control valve section of the tool 10 as embodied inthe hand grip 30, the rear end of the cylinder 34 communicates through apassage 100, which extends along the underneath side of the cylinder,with the interior of the hand grip and, specifically with avalve-receiving bore or chamber 102 provided in the hand grip. The bore102 is of stepped configuration and includes enlarged counterbores 104,106 and 108 of progressively increasing diameter. The counterbore 108 isinternally threaded for reception thereinof a nipple fitting 110designed for attachment to an airhose' 1 12 leading from a source of airunder pressure (not shown).

A spool-type valve body 114 is slidable in the bore 102 and is formedwith an annular flange 116 which normally seats against the annularshoulder which exists between the counterbores 104 and 106, and which isheld thereagainst by a spring 118 which bears at its lower end againstthe nipple fitting 110 and at its upper end against the flange 116. Theupper end of the valve body 114 is provided with an annular sealingflange 120 immediately below which there is a recess 121 which remainsin register with the passage 100 in all positions of the valve body. Thevalve body 114 is provided with an axial bore 122 which communicateswith a series of radial v passages 124, these latter passages remainingat all times in communication with the bore 104 below the level of theflange 116.

The pistol grip 30 is recessed as at to accommodate the trigger 32 andthe latter is mounted for swinging movement about the horizontal axis ofa fixed pin 132 which extends across the recess 130. The upper end ofthe valve body 114 is provided with an attachment post 134. A thrustlink 136 is 3 overhanging edge 1380f the trigger 32 constitutes, ineffect, a 'leverarm adapted to be engaged by the finger of the operatorso that when the trigger is depressed a mechanical advantage is attainedwhereby relatively light finger pressure will displace the valvebodyagainst the action ofthe spring 118.

Considering now the normal operation-of the control valve section 30 ofthe tool,assuming the nipple fitting 110 to be connected. throughthe'airh'ose 112 to .a source of air under adequate pressure toeffectively performa sealin'g'operation by the jaw section42 'upon aseal S, depression of thetrigger 32 will cause the valve body 114 toshift downwardly in the bore 102 to a projected position so that theannular depression previously'described. At this time the sealing flange.120 will I seal the passage 100 from the recessed portion 130' of the 1"hand grip 30. After the sealhas been fully crimped, release of thetrigger 32 will restore the valve body- 114 to its upper position, thussealingoff communication between the counterbore 104 and the airpassagel00- so that .the supply of pressurized air to the cylinder 34 isdiscontinued, whereupon the spring 96 .will restore the piston to itsretractedposition, thereby opening the seal-crimping jaws 16and'releasing the fully crimped seal. Air. in the rear'end of thecylinder will escape to the atmosphere through'the' passage l00,'pastthe spool flange 120 and into the recessed portion of the hand gripwhich is in open communication with the atmosphere. 1

The previously mentioned means for preventing release of the sealingjaws 16. from ,the sealS in the event that for any reason whatsoever, asfor example lack of adequate operating air pressure in the line, thejaws fail to effect full crimping depth upon the seal, comprises alatching member or pawl 150 of spiderlikedesignand which is mounted forrockingmovement on the f xed pin 132. This latching pawl is providedwith a depending radial latch arm or dog 152 designed for cooperationwith'thepost 134 on the valve body 114, a second radial the latchingpawl ina clockwise direction as viewed in FIGS.

1, 3 and 6. I

Referring now to FIG. 1, the lower end region of the radial latch arm ordog 152 of the latching pawl 150 normally bears against the post l34onthe valve body 114 and the extreme lowerendof this arm is stepped toprovide a pair of latching movement of the valve body 114'incidenttodepression of the trigger 32 as previously described, these twoshoulders. 160 and 162 are designed for successive register with theupper end of the post 134 under the influence of the biasing action ofthe compression spring 158. The overall length of the valve body 114 issuch that at no time does it clear the lower end of the latch arm 152but, whenv the'valve body is in'its fully depressed position, theshoulder 162 directly overlies the upper end of the post 134 as shown inboth FIGS. 4 and 6.

In the operation of; the crimping tool 10, assuming for purposes ofdiscussion that-line pressure in the airhose 112 is the upper end of thepost. At this time a point of no return, as far as the trigger 32 isconcerned, is reached and release of finger pressure on the trigger willfail to restore it to its fully retracted position. If the trigger isfully depressed the shoulder 1 62 will latch over the end of the post134. At the same time the sealing flange 120 on the valve body will havemoved to a position where it' seals the passage 100 from the recess 130while at the recessed area 121 of the valve body will have establishedat least partial communication between the bore 104 and the passage 100.Air under pressure will thus be admitted to the rear end of the cylinder134 to drive the piston 44 forwardly and close the crimping jaws 16 uponthe seal S in the manner previously described. At a predetermined pointin the travel of the piston the crimping jaws 16 will initially engagethe flanges 18 of the seal S as shown in FIG. 5. Because the seal iscomprised of relatively heavy gauge steel while air pressure in thecylinder 34 is below the requiredv pressure, the reaction force of theseal against the jaws will produce a condition of stall wherein theparts assume substantially the positions in which they are shown in FIG.5. If air pressure is extremely low, no deformation whatsoever of theseal flanges will take place and the shoulder 162 will remain effectiveto prevent return of the valve body 114. At higher pressures a partialdeformation of the seal flange 18 may occur, as well as some deformationof the strapping laminae 12 and 14, thus allowing the piston 44 totravel slightly further forwardly in the cylinder 34. The distance whichthe piston 44 will travel forwardly in the cylinder 34 will be afunction of seal resistance coupled with available air pressure but, inany event, release of the trigger 32 will be ineffective to stop the airsupply to the 1 rear end of the cylinder 34 until such time as thepiston reaches the end of its forward stroke and engages the abutment154 of the latching pawlv 150 and thus swings the latch arm 152 out ofthe path of return movement of the valve body 114 so that the latter mayreturn to its fully retracted position under the influence of the spring118. with the valve body 114 thus in its original position, the rear endof the cylinder 34 is bled to atmosphere while the supply of air to thecylinder is discontinued in the manner previously set forth.

It will be appreciated that since the latching pawl is effective toprevent return of the trigger 32 to its retracted position unble toexert sufficient pressure to complete the crimping shoulders 160 and162. During the progressive downward operation. Under these conditions.the operator is unable to remove the tool from the seal S which, inturn, is loosely held to the strapping against removal despite the factthat the seal remains to be fully crimped. As soon-as the air pressurein the line is restored to its full rated value, the crimping cycle willcontinue to completion from the point at which it was interrupted byreason of piston stall.

The forwardly extending release finger 156 is provided for v the purposeof permitting the operator to kick out the latch arm 136 from itsblocking position with respect to the valve body 114,.thus releasing thejaws 16 from the seal, if full line formed, the edge of themountingplate constituting a reaction shoulder for the prying action ofthe tool. Despite the fact that below that which is required foreffecting a full depth of seal crimp, initial depression of the'trigger32 will exert a downward force upon the valve body 114 through themedium of the thrust link 136 and, as ,the valve body moves downwardly,the latch arm 152 will slide upon the adjacent side of the post. 134until such'time as the upper end of the post encounters the shoulder160, at'which time the biasing in this manner an operator may releasethe tool from the seal for performance of a succeeding sealing operationthe operator is however placed on notice that the seal from which thejaws 16 have just been released is a defective one.

The invention is not to be limited to the exact arrangement of .partsshown in the accompanyingdrawings or described in this specification asvarious changes in the details of construcaction of thespring 158 willcause this shoulder to latch'over tion may be resorted to withoutdeparting from the spirit of the invention. Therefore, only insofar asthe invention has particularly be pointed out in the accompanying claimsis the same to be limited.

I claim:

1. In a fluid-actuated tool for crimping a seal about the overlappingportions of a strapping loop, in combination, a pair of seal-crimpingjaws movable toward and away from each other between a fully closedseal-crimping position and a fully open seal-releasing position, acylinder having a piston reciprocable therein and operatively connectedto said jaws, said piston being movable between a retracted positionwherein the jaws assume their fully open position and an advancedposition wherein the jaws assume their fully closed position, springmeans yieldingly urging the piston to its retracted position, a manuallyoperable control valve in communication with the cylinder and having amovable valve body effective in a projected position to supply air tosaid cylinder to drive the piston to its advanced position and effectivein a retracted position to bleed said cylinder to the atmosphere andallow said spring means to return the piston to its retracted position,a spring yieldingly urging said valve body to its retracted position,releasable latch means for automatically latching upon movement of saidvalve body to its projected position, said latch means in said projectedposition, and means for releasing said latch means when said pistonmoves to its fully advanced position and for returning the valve body toits retracted position whereby said cylinder is bled to the atmosphereand said spring means returns the piston to its retracted position. 2.In a fluid-actuated tool, the combination set forth in claim 1, whereinsaid releasable latch means comprises a movable spring-biased latchmember yieldingly and slidingly bearing against said valve body andhaving a latch shoulder thereon capable of projection into the path ofreturn movement of the valve body when the latter is in its projectedposition, and an abutment finger on said latch member projecting intosaid cylinder and engageable by the piston when the latter moves to itsadvanced position for automatically shifting the position of the latchmember to withdraw the same from said path of return movement.

3. in a fluid-actuated tool, the combination set forth in claim 2,wherein said latch member further includes a release finger by means ofwhich the member may be manually shifted to withdraw said latch shoulderfrom said path of return movement.

4. In a fluid-actuated tool, the combination set forth in claim 1,wherein said releasable latch means comprises a latch member mounted forrocking movement about a fixed axis and having a radial latch dogprojecting alongside the valve body and slidingly engageable therewith,spring means yieldingly biasing said latch member in a direction tomaintain said dog in sliding contact with the valve body, a latchshoulder on said dog capable of projection into the path of returnmovement of the valve body when the latter is in its projected position,and a radial abutment finger on said latch member projecting into saidcylinder and engageable by the piston when the latter moves to itsadvanced position for automatically shifting the latch member in theopposite direction to withdraw said latch shoulder from said path ofreturn movement.

5. in a fluid-actuated tool, the combination set forth in claim 4,wherein said latch member is further provided with a radial releasefinger by means of which the latch member may be manually shifted towithdraw said latch shoulder from said path of return movement.

6. In a fluid-actuated hand tool for crimping a seal about theoverlapping portions of a strapping loop, in combination, a casingdefining a jaw section, a cylinder section and a control valve section,said jaw section including a pair of seal-crimping jaws movable towardand away from each other between a fully closed seal-crimping positionand a fully open seal-releasing position, said cylinder sectionincluding a cylinder, a piston reciprocable in said cylinder andoperatively connected to said jaws and movable between a retractedposition wherein the aws assume their fully open position and anadvanced position wherein the jaws assume their fully closed position,and spring means yieldingly urging the piston to its retracted position,said control valve section being in the form of a hand grip andincluding a valve in communication with the cylinder and having amovable valve body effective in a projected position to supply air tosaid cylinder to drive the piston to its advanced position and effectivein a retracted position to bleed the cylinder to the atmosphere andallow said spring means to return the piston to its retracted position,a spring yieldingly urging the valve body to its retracted position, adepressible trigger effective upon depression'thereof to move the valvebody to its projected position, a latch member pivoted to said casingfor rocking movement about an axis and having a radial latch dogprojecting alongside the valve body and slidingly engageable therewith,spring means yieldingly urging said latch in a direction to maintain thedog in sliding contact with the valve body, a latch shoulder on said dogcapable of projection into the path of movement of the valve body whenthe latter is in its projected position, and a radial abutment finger onsaid latch member projecting into said cylinder and engageable by thepiston when the latter moves to its advanced position for automaticallyshifting the latch member in the opposite direction to withdraw saidlatch shoulder from said path of return movement.

7. In a fluid-actuated hand tool, the combination set forth in claim 6,wherein said latch member is further provided with a radial releasefinger which projects outwardly of the casing and by means of which thelatch member may be manually shifted to withdraw said latch shoulderfrom said path of return movement.

8. In a fluid-actuated hand tool, the combination set forth in claim 7,wherein said casing is provided with a reaction shoulder in the vicinityof the projecting portion of said radial release finger to the end thatthe finger may be manually actuated by the prying action of a toolinserted between the finger and reaction shoulder.

9. In a fluid-actuated hand tool, the combination set forth in claim 8,wherein said trigger is pivoted for rocking movement about the axis ofrocking movement of the latch member, 'and is operatively connected tothe valve body for movement in unison therewith by a thrust link whichis pivoted at one end to the valve member and at the other end to aneccentric point on the trigger.

10. In a fluid-actuated hand tool, the combination set forth in claim 8wherein said valve body is effective in a range of projected positionsto supply air to the cylinder and wherein said latch dog is providedwith a second latch shoulder likewise capable of projection into thepath of movement of the valve body when the latter moves beyond aninitial projected position so that the valve body may be selectivelylatched in progressively projected positions.

1. In a fluid-actuated tool for crimping a seal about the overlappingportions of a strapping loop, in combination, a pair of seal-crimpingjaws movable toward and away from each other between a fully closedseal-crimping position and a fully open seal-releasing position, acylinder having a piston reciprocable therein and operatively connectedto said jaws, said piston being movable between a retracted positionwherein the jaws assume their fully open position and an advancedposition wherein the jaws assume their fully closed position, springmeans yieldingly urging the piston to its retracted position, a manuallyoperable control valve in communication with the cylinder and having amovable valve body effective in a projected position to supply air tosaid cylinder to drive the piston to its advanced position and effectivein a retracted position to bleed said cylinder to the atmosphere andallow said spring means to return the piston to its retracted position,a spring yieldingly urGing said valve body to its retracted position,releasable latch means for automatically latching upon movement of saidvalve body to its projected position, said latch means in said projectedposition, and means for releasing said latch means when said pistonmoves to its fully advanced position and for returning the valve body toits retracted position whereby said cylinder is bled to the atmosphereand said spring means returns the piston to its retracted position. 2.In a fluid-actuated tool, the combination set forth in claim 1, whereinsaid releasable latch means comprises a movable spring-biased latchmember yieldingly and slidingly bearing against said valve body andhaving a latch shoulder thereon capable of projection into the path ofreturn movement of the valve body when the latter is in its projectedposition, and an abutment finger on said latch member projecting intosaid cylinder and engageable by the piston when the latter moves to itsadvanced position for automatically shifting the position of the latchmember to withdraw the same from said path of return movement.
 3. In afluid-actuated tool, the combination set forth in claim 2, wherein saidlatch member further includes a release finger by means of which themember may be manually shifted to withdraw said latch shoulder from saidpath of return movement.
 4. In a fluid-actuated tool, the combinationset forth in claim 1, wherein said releasable latch means comprises alatch member mounted for rocking movement about a fixed axis and havinga radial latch dog projecting alongside the valve body and slidinglyengageable therewith, spring means yieldingly biasing said latch memberin a direction to maintain said dog in sliding contact with the valvebody, a latch shoulder on said dog capable of projection into the pathof return movement of the valve body when the latter is in its projectedposition, and a radial abutment finger on said latch member projectinginto said cylinder and engageable by the piston when the latter moves toits advanced position for automatically shifting the latch member in theopposite direction to withdraw said latch shoulder from said path ofreturn movement.
 5. In a fluid-actuated tool, the combination set forthin claim 4, wherein said latch member is further provided with a radialrelease finger by means of which the latch member may be manuallyshifted to withdraw said latch shoulder from said path of returnmovement.
 6. In a fluid-actuated hand tool for crimping a seal about theoverlapping portions of a strapping loop, in combination, a casingdefining a jaw section, a cylinder section and a control valve section,said jaw section including a pair of seal-crimping jaws movable towardand away from each other between a fully closed seal-crimping positionand a fully open seal-releasing position, said cylinder sectionincluding a cylinder, a piston reciprocable in said cylinder andoperatively connected to said jaws and movable between a retractedposition wherein the jaws assume their fully open position and anadvanced position wherein the jaws assume their fully closed position,and spring means yieldingly urging the piston to its retracted position,said control valve section being in the form of a hand grip andincluding a valve in communication with the cylinder and having amovable valve body effective in a projected position to supply air tosaid cylinder to drive the piston to its advanced position and effectivein a retracted position to bleed the cylinder to the atmosphere andallow said spring means to return the piston to its retracted position,a spring yieldingly urging the valve body to its retracted position, adepressible trigger effective upon depression thereof to move the valvebody to its projected position, a latch member pivoted to said casingfor rocking movement about an axis and having a radial latch dogprojecting alongside the valve body and slidingly engageable therewith,spring means yieldingly urging said latch in a direction to maintaiN thedog in sliding contact with the valve body, a latch shoulder on said dogcapable of projection into the path of movement of the valve body whenthe latter is in its projected position, and a radial abutment finger onsaid latch member projecting into said cylinder and engageable by thepiston when the latter moves to its advanced position for automaticallyshifting the latch member in the opposite direction to withdraw saidlatch shoulder from said path of return movement.
 7. In a fluid-actuatedhand tool, the combination set forth in claim 6, wherein said latchmember is further provided with a radial release finger which projectsoutwardly of the casing and by means of which the latch member may bemanually shifted to withdraw said latch shoulder from said path ofreturn movement.
 8. In a fluid-actuated hand tool, the combination setforth in claim 7, wherein said casing is provided with a reactionshoulder in the vicinity of the projecting portion of said radialrelease finger to the end that the finger may be manually actuated bythe prying action of a tool inserted between the finger and reactionshoulder.
 9. In a fluid-actuated hand tool, the combination set forth inclaim 8, wherein said trigger is pivoted for rocking movement about theaxis of rocking movement of the latch member, and is operativelyconnected to the valve body for movement in unison therewith by a thrustlink which is pivoted at one end to the valve member and at the otherend to an eccentric point on the trigger.
 10. In a fluid-actuated handtool, the combination set forth in claim 8 wherein said valve body iseffective in a range of projected positions to supply air to thecylinder and wherein said latch dog is provided with a second latchshoulder likewise capable of projection into the path of movement of thevalve body when the latter moves beyond an initial projected position sothat the valve body may be selectively latched in progressivelyprojected positions.